Q.: How does cold weather affect concrete curing time and strength? Should cement content be increased in cold weather?
A.: Concrete gains strength more slowly in cold weathers so curing time should be lengthened. ACI committee 302 recommends curing at least 4 days in hot weather or 7 days in weather when temperatures are lower but above 50 degrees F. Curing at temperatures lower than 50 degrees F is not ordinarily recommended but when it is unavoidable it is advisable to prolong the curing period beyond 7 days. If there is danger of freezing, curing blankets or other protection should be provided to retain heat.
Cement content is not ordinarily increased for concreting in cold weather but it is a method which is sometimes used to increase the rate of strength gain and improve the resistance to damage.